Electronic displays are commonly used to provide a visual interface for many electronic devices including laptop computers, cell phones, and other mobile and non-mobile devices. An electronic display may generate visual information by generating light within the display and/or by modulating the light transmitted from the display. Today, the electronic displays commonly found in mobile devices include liquid crystal displays (LCDs) and electronic ink displays.
LCDs utilize the light modulating properties of liquid crystals. Because the liquid crystals inside an LCD do not emit light themselves, an LCD requires an external illumination source such as a backlighting device. Each pixel in an LCD display typically consists of a layer of liquid crystals aligned between a first transparent electrode and a first polarizing filter on one side of the liquid crystal layer and a second transparent electrode and a second polarizing filter on the other side of the liquid crystal layer. The first and second polarizing filters may be arranged such that light passing through the first polarizing filter is completely blocked by the second polarizing filter. If the light is completely blocked, then the pixel will appear black. By controlling the electric field applied across the liquid crystal layer, an LCD can modulate the light that is allowed to pass through the two polarizing filters, thereby creating a display with varying degrees of gray per pixel. In order to provide a color LCD display, each pixel may be further broken up into red, green, and blue subpixels with a red, green, and blue color filter associated with each of the three subpixels, respectively.
Electronic ink displays utilize microcapsules filled with a fluid and charged particles. In one example, a particular microcapsule may be filled with colored oil and charged colored particles. An electrical field may be applied to control the location of the charged colored particles within the particular microcapsule. When the charged colored particles are attracted to the display surface, then a color associated with the charged colored particles will be displayed. When the charged colored particles are moved away from the display surface, then the color of the oil will be displayed. In another example, an electronic ink display may utilize microcapsules that contain positively charged particles of one color and negatively charged particles of another color. In this example, an electric field may be applied to control whether the positively charged particles or the negatively charged particles are attracted to the display surface. The microcapsules used in electronic ink displays are not capable of emitting light and do not allow for a fully transparent display.